During a recent girls’ weekend in Topsail Beach, Kate Combs and her friends spied a wholly unexpected beachgoer.

“On Sunday morning at about 8 a.m., most of us were sleeping, but one girl came in screaming that there was a whale outside,” said Combs, who lives in Hampstead. “So we all got up and ran outside.”

Clustered outside the beach house, Combs and her friends were able to spot the whale’s spout and its tail as it swam past, about 100 yards offshore.

“It was really close, and it was huge,” she said. “All we could really see was its tail, and its tail was enormous.

“It was really cool.”

Seeing a whale up-close in its natural environment can feel like a once-in-a-lifetime experience. But during the next few months, residents and visitors to the North Carolina coast may have multiple opportunities to spot one.

“We know that on any given day from basically November through March and April, we could have right and humpback whales off our coast,” said Ann Pabst, a marine biologist at the University of North Carolina Wilmington, as well as the co-director of the university’s marine mammal stranding program. “We do not have a sense of how many are offshore right now, but we do know that this is an important time when whales are moving through our waters.”

Neither humpback nor right whales live in North Carolina waters on a consistent basis. Both species are migratory, spending their summers in cooler, northern-hemisphere waters and then travelling to warmer, subtropical seas, where they mate, calve and spend the winter.

That travel cycle places the giant mammals — particularly the North Atlantic right whale — near beaches throughout the region for roughly five months out of the year, according to Barb Zoodsma, the southeast right whale recovery program coordinator for the National Oceanic and Atmospheric Administration Fisheries.

“Our understanding was that right whales migrated in the fall and migrated back up in the spring, but now we’re learning that right whales may stay along the coast, and move past the coast, throughout the winter,” she said. “You can expect to see them through April.”

Though both species may be nearby during the same time period, humpback and right whales are fairly easy to tell apart.

Humpback whales, Pabst said, can be identified by their long, white fore-flippers, while right whales are characterized by V-shaped water spouts, broad, flat backs and lumpy patterns on their heads, known as callosities.

Each species has been spotted off nearby beaches in recent weeks. Humpback whales have been confirmed in the waters near Topsail Beach, and right whales have been seen swimming past Wrightsville Beach.

Both right and humpback whales are endangered, making it illegal to be within 500 yards — or 1,500 feet — of either. The right whale is one of the most critically endangered whales in the world, with NOAA estimating the global population at around 400. The slow-moving mammal is particularly vulnerable to ship strikes, prompting NOAA to partner with the Coast Guard in a project known as Operation Right Speed, a five-month period during which vessels of a certain size are required to cruise more slowly.

From Nov. 1 to April 30, “regulations require vessels 65 feet (long) or greater to operate at speeds 10 knots or less in designated right whale migration routes and calving grounds,” according to the Coast Guard.

Those designated routes bubble along sections of the East Coast, including a particularly large corridor that extends from Wilmington past Savannah, Ga.

The speed reduction regulations, in effect since December 2008, are a protective measure, designed to give both whales and ship operators more time to notice and avoid each other — especially around the entrances to deepwater ports, like Wilmington and Morehead City. Because right whales have no dorsal fin and swim close to the surface of the water, they can be particularly difficult to spot, Zoodsma said.

“Many assume that due to their size right whales would be easy to see,” she said. “But just a slight difference in the texture on the water’s surface is often the only clue that a whale is present.”

Right whale

· Large, rotund and black, with large heads and no dorsal fins.

· Characterized by lumpy white growths on their heads, known as callosities.

· Can grow up to 53 feet in length and weigh up to 80 tons.

· Most critically endangered whale in the world, with global population estimates of around 400.

Humpback whale

· Dark grey, with a variable amount of white on fins and belly.

· Characterized by large, white fore-flippers.

· Can grow up to 60 feet long; females are larger than males.

· Males sing complex songs that can last for 20 minutes and can be heard up to 20 miles away.